Patent Document 1 describes an optical branching module for use in the fields such as optical communication. FIG. 5 is a diagram showing a configuration of this optical branching module. This optical branching module 100 includes an optical branching circuit 103, two reflective plates 104a and 104b, and a plurality of optical fibers 105. The optical branching circuit 103 has a configuration in which a plurality of optical branching elements 102, 106, 107a, and 107b are connected in multiple stages through an optical waveguide 101 on a substrate. The reflective plate 104a reflects one light beam branched in the optical branching element 106 back to the optical branching element 107a. The reflective plate 104b reflects the other light beam branched in the optical branching element 106 back to the optical branching element 107b. 